EasyJet will also base a fifth aircraft in Glasgow, creating some 50 jobs among pilots, cabin crew and ground staff.
The news comes after the airline revealed to The Scotsman last year it would expand at Glasgow to redress the balance with Edinburgh, where it has eight based aircraft and more than 40 routes.
The strategy comes in contrast to rivals Ryanair, which significantly cut its Glasgow routes last year, blaming the Scottish Government for not halving air tax as ministers had planned.
EasyJet said of its Glasgow plans: “We plan to add new routes and increase our capacity on some existing routes too where we have seen strong demand.
“We are finalising this programme and will be able to update you further soon."
The year-round Birmingham route, which starts on 29 March next year, will see EasyJet compete with Flybe with an average of two flights a day.
The latest expansion follows twice-weekly flights to Venice being launched last October, and an extra weekly flight to Bristol introduced last month.
EasyJet’s maiden flight was from Luton to Glasgow in 1995, and it has flown more than 34 million passengers to and from the west coast airport since.
The airline has more than 1m passengers a year on 19 routes there, which account for one in ten of Glasgow’s total
UK country manager Ali Gayward said: “EasyJet has selected Glasgow as the focus of its growth in Scotland and we are excited about the future at Glasgow.
“The addition of another aircraft will help us to deliver long-term, sustainable growth at the base, providing customers with a greater range of destinations, all with low fares and great service.”
Ms Gayward said the Birmingham route would “provide even more great value and convenient domestic connectivity”.
Easyjet said the route was being introduced “following very strong customer demand for increased connectivity to the Midlands”.
The move comes as the Scottish Government’s new transport strategy only stated it recognised the importance of UK air routes “where rail is not a real alternative for businesses, such as to the south west of England”.
However, Easyjet - in a veiled reference to Flybe - said it was more efficient than other airlines, flying fuller, newer and more fuel-efficient planes.
It said: People have a choice in how they travel and many more people are now thinking about the potential carbon impact of different types of transport
"Many people think that airlines are the same. They’re not.
"The aircraft we fly, the load factor [proportion of seats filled] and the way we fly them means that we are more efficient than many other airlines."
Francois Bourienne, chief commercial officer for Glasgow’s owner, AGS Airports Group, said: “Both EasyJet and Glasgow Airport have enjoyed a long and productive relationship since the airline’s inaugural flight landed here almost a quarter of a century ago.
“This is a significant investment.
“The additional aircraft not only puts Glasgow Airport on a course for future growth, but also underlines EasyJet’s continued commitment to our passengers.
“The introduction of EasyJet’s new Birmingham route is also welcome news as services to England’s second biggest city continue to be very popular with both our business and leisure customers.”