An ironic twist deprived President Reagan of a clear foreign policy triumph at the summit meeting here in Ottawa. For the president did brilliantly in defending American economic policy against such heavy-hitters as Chancellor Helmut Schmidt of West Germany, President Francois Mitterrand of France and Prime Minister Pierre Elliott Trudeau of Canada.

But a sudden burst of tension put the Middle East front and center at the summit. So there emerged, at a time of true danger, when it is particularly difficult to deal with Israel's Prime Minister Menachem Begin, new doubts about the president's own grasp in foreign policy and about the status of his chief advisers.

Daily appearances here gave fresh evidence of a lack of settled order in relations among presidential counselor Edwin Meese, Secretary of State Alexander Haig and National Security Adviser Richard Allen. The three men briefed journalists on all kinds of foreign policy questions in a fashion so random that there seemed no formal lines of authority.

Unwillingness to seem critical of Israel made up the distinctive note in all their comments. At a time when the Israelis were responding to Palestinian attacks from south Lebanon by bombing the daylights out of Beirut, the president's policy advisers talked as though nothing much was amiss.

"We're very hopeful that a cease-fire will result," Allen said a few hours after Prime Minister Begin put off for a full day an urgent cease-fire plea from the roving ambassador Philip Habib. A couple of hours after Begin posponed, Meese announced, as if it could go either way, that the president would shortly make a decision regarding delivery of 10 F16 fighter planes previously earmarked for Israel. Finally, when the decision to suspend delivery of the planes was announced, Secretary Haig said: "This is not a decision that is linked to any specific action on the part of the government of Israel."

But why this superhuman effort to not pass judgment on Israel? The main reason is to make it seem that the president is making all the decisions without any push or tilt from his advisers.

Absolute compartmentalization results from such procedures, and Ottawa provided a striking example. In handling summit discussions on the Middle East on theone hand, and the situation between Israel and Lebanon on the other hand, the United States looked almost schizophrenic.

Secretary Haig and the other foreign ministers began talking about the Middle East when they arrived in Ottawa on July 19. The Europeans sought a joint statement condemning the Israeli attacks on Beirut. Haig prevailed on his colleagues to issue a totally bland statement. It said the seven countries were "distressed by the scale of the destruction," and it called on all "parties ot exercise restraint." The French Foreign Minister, Claude Cheysson, was so disgusted by the weakness of the declaration that he revealed publicly that France had sought a statement much tougher on the Israelis.

While the anodyne statement was evolving, the president and his advisers were also considering action to back up Ambassador Habib's negotiations for a cease-fire between Israel and Lebanon. The decision to suspend plane deliveries was made in that context, and published a couple of hours after the anodyne joint statement was issued. There seemed to be no link between the two lines of action.

Everybody, in consequence, was dissatisfied. The joint statement disappointed the Arabs and their friends in Europe. Suspension of plane deliveries put Begin up against the wall. He replied, predictably, by saying that he would agree to a cease-fire if the United States could also negotiate an accord with Lebanon. That is practically impossible because the regime in Beirut cannot control the Palestinians. Indeed, the Palestinians are now tempted to attack the Israelis in order to provoke an exaggerated retaliation that would discredit Begin still further.

A far better outcome would have been possible if the United States had joined the Europeans in a strong condemnation of the Israeli raides. That would have served as a warning to Begin. Fear that suspension of the plane delivery would follow might have induced him to take a more positive approach to a cease-fire. If it didn't, the United States could have then suspended the plane delivery -- leaving the next move up to Begin.

As it is, a genuine crisis seems to be building. Begin is angry, and the Palestinians are on the warpath. The United States has thrown away a card it should have held in reserve. For all his success in defending economic policy here, Reagan on the Middle East is perceived as no Tallyrand. Indeed, it is hard to see how the administration can manage security affairs until the president decides to place faith in a single official who knows the full range of foreign policy issues.