The House Appropriations Committee, in the first substantive vote of the year on President Reagan's budget, yesterday rejected his proposals to cut back college student loans and to start dismantling the main federal housing program for the poor.

It also rejected, 27 to 22, a move to drop funding for the B1 bomber, which Rep. Sidney R. Yates (D-Ill.) proposed as "the first constructive step" in cutting spending and getting deficits under control.

In a series of votes, the committee approved stopgap funding through Sept. 30 for seven government departments for which regular approprations have not been passed, and then approved billions of dollars worth of "urgent" supplemental appropriations for activities ranging from railroad bridge construction to the Coast Guard.

Among the major spending addons were $321.8 million on top of Reagan's $978.2 million request for student loans, amounting to a rejection of Reagan's proposal to curtail loans to graduate students and to cut other aspects of the student loan program.

The committee also denied all but $100 million of the $9.4 billion he requested in rescissions of past housing appropriations; those rescissions would wipe out about 50,000 new units in the funding pipeline. The $9.4 billion was approved by Congress last year. Reagan has also proposed that there be no further subsidized housing construction in future years.

The committee's actions came as jockeying continued over the apparent stalemate in developing a bipartisan alternative to the president's budget, which Congress is scrambling to rewrite--so far without much success--to reduce its huge projected deficits over the next several years.

In what some took to be a conciliatory sign from the White House, House Speaker Thomas P. O'Neill Jr. (D-Mass.) told reporters that White House chief of staff James A. Baker III wants to meet with the Democratic chairmen of the House budget and tax-writing committees to discuss possible compromises.

O'Neill said Baker called him on Monday to seek meetings with the two chairmen, James R. Jones (D-Okla.) of Budget and Dan Rostenkowski (D-Ill.) of Ways and Means. O'Neill said he and the two chairmen assented to Baker's request but insisted that the full House leadership be kept apprised of the talks.

While he said the Democrats are willing to talk, O'Neill questioned whether such talks would produce results until Republicans take the initiative in proposing changes, and Reagan signals a willingness to compromise.

White House officials, for their part, said carefully that the meetings were instigated by House Republican leader Robert Michel (R-Ill.) and cautioned against regarding them as an indication of retreat.

Said O'Neill: "I would hate to believe we'd go the way of a John Wayne movie and think that compromise is retreat. They (the Republicans) are in control of this government . . . . Let them bring forth a bill and let us have an opportunity to look at it."

Rostenkowski also appeared skeptical whether anything can be achieved until Reagan himself proposes a compromise. An aide said Rostenkowski would be happy to talk with any White House officials but added: "He will not move until Ronald Reagan's signature is above his on anything."

O'Neill issued a statement laying out two fundamental bargaining points for the Democrats that avoided any specific flashpoints for the White House, although they suggest priorities in taxing and spending policy that may make bargaining difficult. He said any agreement would have to include measures that would "put the country back to work" and overcome problems of "fairness" that arose out of last year's action on taxes and spending cuts.

In the Senate, Majority Leader Howard H. Baker Jr. (R-Tenn.) suggested that it was time for Reagan and O'Neill to agree to sit down and talk.

"It is essential that the speaker be part of the arrangement if it is going to go," said Baker, who last week joined with Michel in shifting the focus of budget negotiations from the Republican-controlled Senate to the Democratic House.

Baker's comments appeared to reflect growing feeling in the Senate that Republicans there have gone about as far as they can in pushing for compromise and that Reagan and O'Neill now hold the keys to an agreement.

As of now, said Senate Budget Committee Chairman Pete V. Domenici (R-N.M.), "I don't think anyone around here knows what the magic is that will put it all together."

The stopgap funding bill, or "continuing resolution," which is needed to extend temporary funding authority that expires March 31, is expected to come to the House floor today. The supplemental appropriations will follow, probably later in the week. The two measures were kept separate to avoid any holdups in funding such as the one that closed down the government for a day late last year.

In debate over the supplemental money bill yesterday, the committee rejected a proposal by Rep. William H. Gray III (D-Pa.) to delete $5.5 million that the Coast Guard could use for interdiction of Haitian refugees outside of U.S. territorial waters. Gray contended that such efforts last year resulted in capture of only two vessels containing 162 refugees, amounting to a cost of $2.7 million per vessel and $31,000 per refugee.