Rep. Toby Moffett (D-Conn.) yesterday scored a surprise upset over three more senior members of the House Government Operations Committee to win the chairmanship of the wide ranging environment, energy and natural resources subcommittee.

Moffett defeated Reps. Glenn English (D-Okla.), Elliott Levitas (D-Ga.) and David W. Evans (D-Ind.) to win the subcommittee. The subcommittee was chaired previously by Rep. Leo Ryan (D-Calif.), who was killed while investigating the Peoples Temple cult in Guyana.

Government Operations is a committee devoted to oversight and investigation of government agencies and programs, a function that has been given heavy emphasis by the congressional leadership of both parties in this austerity Congress.

Moffett, a liberal activist elected in 1974, gained a reputation during the last session's work on the energy bill as a gadfly against gas deregulation and the oil companies. Moffett said he would use the subcommittee to look into the United States' lack of preparedness for the crisis in Iran, currently causing oil dislocations, and oversight of such legislation as the toxic substances and clean air bills.

Moffett said he would like to look into oil pricing but only after consulting with Rep. John Dingell (D-Mich.), chairman of an energy subcommittee of Commerce on which Moffett also serves.

Moffett's surprise win marks the second time in two days that the seniority system has been overturned in filling subcommittee chairmanships. Rep. Henry Waxman (D-Calif.) defeated veteran Rep. Richardson Preyer (D-N.C.) in a hard-fought battle for the health subcommittee of Commerce.

Like Waxman, Moffett is a member of the class of '74, a post-Watergate group that came in determined to overturn the seniority system and a class that has remained unique in its willingness to buck tradition.

Unlike Waxman, Moffett said yesterday he kept his race very quiet because "I didn't want to wake up the oil lobby." He said he had not even informed Government Operations Committee Chairman Jack Brooks of Texas of his intentions.

Moffett attributed his win to campaigning hard on the contention that he had expertise in energy matters. He also noted that although the three he defeated were senior to him on the committee, they were elected in the same year.

Moffett said his victory showed that "under the new rules you can win if you have a background in your subject."

Moffett also said members of his subcommittee, Reps. Andrew Maguire (D-N.J.), Robert Drinan (D-Mass.) and Waxman, helped in his campaign.

The subcommittee could be one of the most active and controversial in the House since almost all of the Democratic members are considered quite liberal.

Meanwhile, the House International Relations Committee elected Rep. Stephen J. Solarz (D-N.Y.) to fill the chairmanship of the Africa subcommittee vacated by Rep. Charles Diggs (D-Mich.), who decided not to run for it after being convicted of accepting kickbacks.

Rep. Don Bonker (D-Wash.) became chairman of the subcommittee on international organizations.

And the committee abolished a subcommittee on international development.