The members of Maryland's House of Delegates, who less than a month ago seemed to have assured themselves the maximum possible pay increase, may end up cutting back on their raises.

By a 4-to-1 vote yesterday, the influential House Rules Committee agreed to endorse a Senate-passed measure setting lawmakers' salaries at $16,000 in each of the next four years. The proposal is expected to come up for a vote on the House floor later this week.

The legislators' salaries currently are set at $12,500 annually, and are designed to cover only the three months of the year when the legislature is in session. A state commission recommended last fall that salaries be increased to $16,000 next year and then pushed up to $18,500 by 1982.

If the Senate's $16,000 resolution for the full four years is not approved by a majority of delegates, the higher commission-recommended raises automatically go into effect. Last month, when a majority of delegates failed to approve any of 10 alternate resolutions, it seemed that the lawmakers had succeeded in winning their pay raise by voting against it.

Yesterday's Rules Committee vote, however, seemed to indicate that a majority of delegates could be put together to back the lower $3,500 pay raise.