prime time 
noun
The time at which a radio or television audience is expected to be at its highest: the show is networked at prime time [as modifier]: prime-time television...
- The study, carried out by Leicester University, found that alcohol appears every eight minutes in prime-time television soaps.
- But those seeking a shift to higher-quality programming on prime-time television are likely to be disappointed.
- Lots of other reporters were arriving at this early hour for their prime-time spots.
- the big screen
- the Big Smoke
- the big stick
- the Big Three (or Four etc.)
- the bird has flown
- the birds and the bees
- the biter bitten (or bit)
- the Blessed Sacrament
- the Blitz
- the bloom is off the rose
- the Boat Race
- the body beautiful
- the Book of Psalms
- the Books of the Maccabees
- the boot (or shoe) is on the other foot
- the Border
- the Borders
- the bottom falls (or drops) out
- the Bourse
- the boy (or girl) next door
- the brass ring
- the bread of life
- the breath of life
- the buck stops here (or with someone)
- the Burse