In the late 18th century Bostonians arrived at the theater around 6 p.m. and stayed through a full-length production of an English play and numerous divertissements: dancing, pantomimes, circustype acts. The 1790 Federal Street Theater held two to three thousand spectators and offered a new billing every three or four nights--all for a city of 20,000 inhabitants! This sense of spirited theater is what New England Dinosaur intends to rekindle Saturday and Sunday nights at First Congregational Church, Cambridge. The event begins at 6 p.m. with dance works by Toby Armour, founder of the Boston troupe, Jean Churchill, its current director, and New York avant-gardists Trisha Brown and James Waring; a play, "Gutta Dance", follows. A dinner break is promised (about an hour, long enough for a picnic in or a dash out), and so is rousing camaraderie.

New England Dinosaur, May 8 and 9, 6 p.m., First Congregational Church, 11 Garden St., Cambridge. Tickets $3.

Dance Collective, a loose consortium of Boston choreographers, will put on two concerts in the next week. Tonight and tomorrow night dance works choreographed by four members of the collective and video works created in conjunction with the WGBH New Television Workshop will be performed at the Institute of Contemporary Art, 955 Boylston. (Take the Dudley Sq. bus from Harvard Sq. to the Auditorium MBTA stop.) Next week, May 14 and 15, the group teams with Mass College of Art to present three old works and two untitled premieres. Dance Collective members are strong performers, and they're getting stronger as choreographers.

Dance Collective, May 6 and 7, 8:30 p.m., Institute of Contemporary Art, 955 Boylston St., Boston. Tickets $3.50.

Also, May 14 and 15, 8:30 p.m., Longwood Theater, Mass College of Art, 364 Brookline Ave., Boston. Tickets in advance $3 (call 862-8734) or $3 50 at door.

The year before last Harvard dance rented Peabody School's auditorium for a spring concert. This week the Harvard-Radcliffe Dance Company tiptoes closer to Harvard proper and stages a concert Friday through Sunday nights at the Hasty Pudding theater. The concert pulls together the work of the company's first year, including dances choreographed by Jack Moore and Liz Rosner, guest instructors with the Harvard-Radcliffe Dance Program, by three outside students with the program, and by Harvard senior Andrew Borg.

Claire Mallardi, director of the program and the company's artistic advisor, talked the other day about "bending students' imaginations," encouraging pieces with more depth than the usual student-choreographed works. From glimpses of rehearsal it seems she's succeeded.

Harvard-Radcliffe Dance Company, 8:30 p.m., May, 7-9, Hasty Pudding theater. Tickets $2.50 and $1.50 at Holyoke Center and the door.